As we all know, sunlight is recognized as the main source of vitamin D, and more than 90% of vitamin D in human body comes from sunlight. It is necessary to increase sunlight exposure to prevent osteoporosis.
What is its principle? Ultraviolet rays in the sun can act on human skin, so that 7- dehydrocholesterol can be converted into vitamin D3, which is absorbed into the blood and metabolized by the liver and kidney to become active vitamin D.
So, when should we bask in it? How long will it take? What should I pay attention to? In fact, how to bask in the sun can really prevent osteoporosis? Sunbathing is really a "technical job".
Ultraviolet index
First of all, we need to know the ultraviolet index of sunlight, which refers to the degree of possible damage to human skin caused by ultraviolet radiation in the sun rays reaching the earth's surface when the sun is at the highest position in the sky (usually around noon, that is, from 10 to 3 pm). The variation range of the ultraviolet index is indicated by the number 0- 15. Usually, the ultraviolet index is 0 at night, and it is 15 in tropical, plateau and sunny days. The higher the UV index, the more serious the erythema damage to human skin caused by UV radiation. Similarly, the higher the ultraviolet index, the greater the damage to the skin in a short time.
Studies have shown that vitamin D can only be produced when the ultraviolet index is higher than 3.
The best time to bask in the sun
Generally, it is from 10 to 10 in spring and autumn, from 9 to10 in summer, and from 1 1 2 in winter.
3 pm to 4 pm is also the best time to bask in the sun, which can promote the absorption of calcium and phosphorus in the intestine, enhance physical fitness and promote normal calcification of bones.
Sunbathing place
Due to the low outdoor temperature, sometimes windy, and the inconvenience of the elderly, some people like to bask in the sun through the glass in the house. Although they can feel the warmth through the glass, the glass window blocks the band of synthesizing vitamin D and fails to achieve the purpose of synthesizing vitamin D.
Studies have shown that the transmittance of ultraviolet rays in the required band through the window glass is less than 50%, and it can be reduced to 2% when it is 4 meters away from the window outdoors. Therefore, even if you have to bask in the sun indoors for various reasons, you must open the window and let the sun directly contact your skin.
Sunbathing part
Get more sun on your hands, feet and back.
People who are afraid of sunburn can directly reach out their hands and feet or sunbathe on their backs. No matter which part of their skin, as long as they sunbathe directly with solar energy, they can have the same effect.
At the same time, drying hands and feet can also drive away cold, which is good for joints.
Sunbathing the back can dispel the cold of the spleen and stomach, help improve the digestive function, dredge the back meridians, and be beneficial to the heart and lungs.
Optimum intensity of sunbathing
Each sunbathing time should not be too long, and the time can be gradually increased from 5 10 minutes. Those who are weak should try not to sunbathe for more than 30 minutes.
You can get the required vitamin D by sunbathing10 for 20 minutes every day, which is shorter for children and longer for the elderly, but it is generally recommended to control it within 30 minutes to avoid sunburn.
People living in high altitude and long-term low-level hypoxia environment need to extend the sun exposure time to 30-60 minutes every day, because hypoxia itself will aggravate bone loss. The amount of ultraviolet rays in winter sunshine can be reduced to 1/6 in summer, and the duration of sunshine can be prolonged as much as possible.
How to grasp time needs to vary from person to person. According to skin color and age, people with dark skin color and obese people need more than twice as long.
The best posture to bask in the sun
If you have to choose the best posture for sunbathing, it is-exposure! The reason is that ultraviolet rays must be in close contact with the skin to play their due role.
The less clothes, the greater the exposed area of the skin, and the more vitamin D is synthesized, so if the environment permits, try to wear less clothes.
Dress code for sunbathing
Don't wear white clothes to bask in the sun: white clothes will reflect ultraviolet rays to your face or bare arms, and your skin will be easily hurt, especially in summer when ultraviolet rays are strong.
It is best to wear red clothes when basking in the sun, because the long-wave radiation of red clothes can quickly "eat" the short-wave ultraviolet rays with strong lethality.
Proper sun protection
Excessive ultraviolet rays in the sun can also increase the risk of cataract. When you are in the sun, don't forget to wear sunglasses to block the light from your eyes. You can also wear a hair cap to avoid sunburn.
Women can cover their faces if they don't want to get tanned. If you spend a long time sunbathing, you need to apply sunscreen after sunbathing for a while to prevent sunburn.
Sunbathing cultivation of gourmets
Sunbathing sometimes causes solar dermatitis. Eating some foods in the sun can easily cause photosensitivity, drug eruption or solar dermatitis, so it is best not to eat these foods before supplementing calcium in the sun.
Photosensitive foods such as Chinese cabbage, amaranth, celery, rape, spinach, Chinese cabbage, lettuce, mustard, buckwheat, snail, lemon, mango, and traditional Chinese medicines such as thiazide diuretics and Psoralea corylifolia will enhance their sensitivity to light, and people with allergies are more prone to photosensitive dermatitis.
Kiwi, strawberry, tomato, papaya, nuts, coix seed, green tea, etc. all have different degrees of "sun protection" effect, and eating more is good for the skin.
Precautions for sunbathing
After sunlight, the blood flow of the skin and its subcutaneous tissue will increase obviously, which will be increased by heating and sweating, so the effective blood volume in the corresponding blood is relatively insufficient, which is easy to cause dehydration and even syncope, especially for the elderly and infirm, and it is necessary to replenish water in time to avoid dehydration.
It is not advisable to bask in the sun on an empty stomach after breakfast 1 hour.